In so-called hot-fill packages, a container is filled with hot fluid product and capped while the fluid product is still hot. As the fluid product cools, a reduction in fluid volume creates a vacuum within the package—i.e., an internal pressure within the package that is less than the surrounding atmospheric pressure. Vacuum panels typically are provided in the container sidewall to flex inwardly and thereby to relieve the vacuum pressure within the container. A general object of the present invention is to provide a molded plastic container that is particularly well adapted for such hot-fill applications.
The present invention embodies a number of aspects, which can be implemented separately from or more preferably in combination with each other.
A plastic container in accordance with one aspect of the present invention has at least one vacuum panel for absorbing sub-atmospheric pressure within the container. The vacuum panel has a periphery, an outwardly convex central portion and an outwardly concave intermediate portion that connects the central portion to the periphery. The central and intermediate portions are such as to resist inversion of the central portion of the panel, from an outwardly convex configuration to an outwardly concave configuration, at least to an internal vacuum level of 6 psi within the container (i.e., 6 psi below atmospheric pressure). The central portion of the vacuum panel preferably is oval, and may be provided with molded-in indicia that strengthen the central panel portion and further resist inversion under vacuum. The outwardly convex central portion preferably has a radius of curvature as viewed from an axial direction in the range of 0.6 to 0.75 inch, and a radius of curvature as viewed from a tangential direction in the range of 3 to 5 inches. The outwardly concave intermediate portion of the vacuum panel preferably has a radius of curvature as viewed from an axial direction in the range of 0.175 to 0.25 inch, and a radius of curvature as viewed from a tangential direction in the rang of 0.6 to 0.75 inch. These radii of curvature are such that the central portion of the panel does not invert under vacuum within the container.
A hot-fill container of one-piece plastic construction in accordance with another aspect of the present invention includes a base, a neck finish and a cylindrical body connecting the base to the neck finish. The cylindrical body has an upper portion adjacent to the neck finish and a lower portion adjacent to the base. The upper portion of the cylindrical body includes a label panel for securing a label to the container. The lower portion of the container body includes a series of circumferentially spaced ribs, and a series of vacuum panels connected between the ribs. Each of the vacuum panels has an outwardly convex central portion and an outwardly concave intermediate portion that connects the central portion to the ribs. In differing embodiments of the invention, the ribs are either parallel to or at an angle to the central axis of the container. Indicia, such as a logo, may be molded into the central portion of each vacuum panel, which strengthens the central portion of each vacuum panel and resists inversion of each central portion to a concave configuration under hot-fill vacuum within the container.